/Engine/Source/Runtime/CoreUObject/Public/Misc/PackageName.h
Checks if the package exists on disk.
true if the specified package name points to an existing package, false otherwise.
static bool DoesPackageExist ( const [FString](API\Runtime\Core\Containers\FString) & LongPackageName, [FString](API\Runtime\Core\Containers\FString) * OutFilename, bool InAllowTextFormats )